The latest technical advances in the medical field include the development over the last 20 years of procedures for operating on the eyes of patients suffering from myopia or hyperopia. Different methods and special instruments have been designed for performing this kind of surgery. One such instrument is a mechanical device bearing a cutting element for performing the operation of resection on the cornea of the eye. There are currently a few of these devices on the market. Known as microkeratomes (MKM), they are suitable for performing Myopic Keratomileusis-In-Situ and Hyperopic Lamellar Keratotomy. In all these devices the cutting element is moved by an electric or turbine motor. This movement is a transverse motion with respect to the direction of the cutting path. It is therefore necessary to push the blade-carrying device manually in order to make the cut. Surgical operations of this kind are presently performed in this manner, and though they have been quite successful, they involve some problems yet to be solved.
To obtain a precise correction of a visual defect, the dimensions of the resection that is made must be very precise. Since resecting is done manually, the precision of the resection depends on factors difficult to control, such as the pressure exerted by the surgeon's hand on the instrument and hence on the patient's eye, or the speed with which he pushes the instrument and its blade to make the resection. The higher the speed, the thinner the section will be, resulting in hypocorrection, and the lower the speed, the thicker the resection will be, resulting in hypercorrection. Moreover, since the sliding parts of the mechanical instrument are finely adjusted, irregular pressure or speed applied by the surgeon to the instrument may cause it to bind. The cutting would then be irregular and would produce irregular astigmatism in the patient's eye. Likewise, irregular pressure on the instrument and on the eye will affect the dimension of the resection.